Nutrition and health

Objectives:
Diabetes prevention is a public health priority. Vitamin D supplementation may help prevent the development of diabetes in persons at increased risk. Therefore, this review article has been conducted.

Does vitamin D supplementation reduce risk of type 2 diabetes?

Study design:
This review article included 28 RCTs with 3,848 participants.

The sample size varied from 23 to 511.
The mean age of participants ranged from 26 years to 71 years.
The duration of follow-up across studies ranged from 2 months to 5 years, with a median follow-up of 22 weeks [interquartile range (IQR): 14 to 48 weeks], a duration long enough to detect changes in measured outcomes.

The average vitamin D supplementation dose of 88 µg/d (3500 IU/d).
All included trials measured the effect of vitamin D supplementation on serum 25(OH)D concentrations.

Results and conclusions:
The investigators found overall, serum 25(OH)D concentrations in the treated arms (vitamin D-supplemented groups) significantly improved by 45.1 nmol/L [95% CI = 41.3 to 48.9, p 0.001, I2 = 97.4%].

The investigators found compared with the control group, vitamin D supplementation significantly reduced HbA1c level by -0.48% [95% CI = -0.79 to -0.18, p = 0.002, I2 = 92.1%].
However, after adjusting the effect size for potential publication bias using the “trim and fill” method, 4 potentially missing studies were imputed in the funnel plot and the effect size increased from -0.48% [95% CI = -0.79 to -0.18] to -0.71% [95% CI = -1.02 to -0.39].

The investigators found compared with the control group, vitamin D supplementation significantly reduced fasting plasma glucose level by -0.46 mmol/L [95% CI = -0.74 to -0.19, p = 0.001, I2 = 92.4%].  
However, after adjusting the effect size for potential publication bias using the “trim and fill” method, 6 potentially missing studies were imputed in the funnel plot and the effect size increased -0.46 mmol/L [95% CI = -0.74 to ­0.19] to -0.72 mmol/L [95% CI =-1.02 to -0.42].

The investigators found compared with the control group, vitamin D supplementation significantly reduced HOMA-IR level by -0.39 [95% CI = -0.68 to -0.11, p = 0.007, I2 = 91.3%].
However, after adjusting the effect size for potential publication bias using the “trim and fill” method, 5 potentially missing studies were imputed in the funnel plot and the effect size increased from -0.39 [95% CI = -0.68 to -0.11] to -0.62 [95% CI = -0.92 to -0.32].

The investigators found in subgroup analysis both HbA1c and HOMA-IR showed a greater reduction over time among overweight/obese individuals compared with prediabetics [HbA1c = -0.98 ± 0.45 vs -0.29 ± 0.14, p = 0.1 and HOMA-IR = -0.62 ± 0.23 vs -0.07 ± 0.16, p = 0.05].

The investigators found in subgroup analysis vitamin D supplementation significantly decreased HbA1c [p = 0.05], fasting plasma glucose level [p = 0.05] and HOMA-IR [p = 0.1] to a greater extent when serum 25(OH)D concentration achieved was above 86 nmol/L.

The investigators found in subgroup analysis vitamin D supplementation for less than 6 months provided a larger effect size on HbA1c in comparison with long durations [-0.75 ± 0.33 vs -0.25 ± 0.11, p = 0.1].

The investigators found in subgroup analysis HbA1c showed greater improvement in populations with a mean age younger than 45 years in comparison with older populations [-1.15 ± 0.6 vs -0.30 ± 0.1, p = 0.05].

The investigators found in subgroup analysis greater reductions were found within HbA1c and fasting plasma glucose levels when baseline (at the beginning of the study) mean serum 25(OH)D concentration was ≥50 nmol/L, whereas the lowering effect was significantly less in the subgroup with baseline mean 25(OH)D 50 nmol/L [HbA1c = -0.79 ± 0.25 vs -0.14 ± 0.13, p = 0.04 and fasting plasma glucose level = -0.69 ± 0.21 vs -0.11 ± 0.10, p = 0.05].

The investigators concluded 88 µg/d vitamin D supplementation during 22 weeks improves glycemic measures and insulin sensitivity and may be useful as part of a preventive strategy for type 2 diabetes, particularly among overweight/obese individuals younger than 45 years.

Original title:
Vitamin D Supplementation, Glycemic Control, and Insulin Resistance in Prediabetics: A Meta-Analysis by Mirhosseini N, Vatanparast H, [...], Kimball SM.

Link:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6016617/

Additional information of El Mondo:
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HbA1c, FPG, HOMA-IR and plasma glucose after 2-hour oral glucose tolerance test (2HPG) are different parameters associated with (pre)diabetes.

 

Objectives:
Has flavonoid supplementation potential against obesity?

Study design:
This review article included 58 RCTs.
Analysis endpoints were calculated as the mean difference between baseline and post-treatment.
Flavonoids were in subclasses of flavanols, flavonols, isoflavones, flavanones, anthocyanins and proanthocyanidins. They were mostly in the form of supplements and dosages varying from 40 to 1300 mg/day.

Results and conclusions:
The investigators found among flavonoid subclasses, flavanols showed potential for decreasing BMI, in the overall population [MD = -0.28 kg/m², p = 0.04, n = 21] and in the subgroups of Asians [MD = -0.42 kg/m², p = 0.046, n = 13], ages 50 years [MD = -0.50 kg/m², p = 0.008, n = 14], BMI ≥25 kg/m² [MD = -0.30 kg/m², p = 0.049, n = 15] and at doses ≥500 mg/day [MD = -0.36 kg/m², p = 0.049, n = 12].

The investigators found among flavonoid subclasses, isoflavones also significantly decreased BMI of non-Asian populations [MD = -0.26 kg/m², p = 0.035, n = 13] and doses ≥75 mg/day [MD = -0.34 kg/m², p = 0.027, n = 8].

The investigators found in the overall assessment, flavanols also significantly decreased waist circumference [MD = -0.60 cm, p = 0.02, n = 18] but had no significant effect on body fat percentage.

The investigators found the available trials did not reveal significant effects from flavonols, flavanones and anthocyanins on the specified anthropometric measures.

The investigators concluded that flavanols, particularly ≥500 mg/day and isoflavones, particularly ≥75 mg/day have potential against obesity.

Original title:
Flavanols are potential anti-obesity agents, a systematic review and meta-analysis of controlled clinical trials by Akhlaghi M, Ghobadi S, […], Mohammadian F.

Link:
https://www.ncbi.nlm.nih.gov/pubmed/29759310

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Objectives:
Carbohydrate-restricted diets may increase low-density lipoprotein cholesterol (LDL-cholesterol or bad cholesterol) and thereby cardiovascular risk. Therefore, this review article has been conducted.

Do carbohydrate restriction diets increase cholesterol and triglycerides levels in overweight/obese adults?

Study design:
This review article included 8 RCTs with a total of 1,633 participants, of which 818 in carbohydrate-restricted diet group (intervention group) and 815 low-fat diet group (control group).

All RCTs had more than 100 participants with duration of at least 6 months.

Results and conclusions:
The investigators found when compared with low-fat diets, carbohydrate-restricted diets showed no significant difference in LDL-cholesterol levels after 6, 12 and 24 months.
Although an overall pooled analysis statistically favoured low-fat diets [0.07 mmol/L, 95% CI = 0.02-0.13, p = 0.009], this was clinically insignificant.

The investigators found when compared with low-fat diets, carbohydrate-restricted diets significant increased HDL-cholesterol (good cholesterol) levels [0.08 mmol/L, 95% CI = 0.06-0.11, p 0.00001] after 6 and 12 months.
These favourable changes were more marked in the subgroup with very-low carbohydrate content [50 g/d: 0.12 mmol/L, 95% CI = 0.10-0.14, p  0.00001].

The investigators found when compared with low-fat diets, carbohydrate-restricted diets significant reduced plasma triglycerides levels [-0.13 mmol/L, 95% CI = -0.19 to -0.08, p  0.00001 after 6 and 12 months.
These favourable changes were more marked in the subgroup with very-low carbohydrate content [50 g/d: -0.19 mmol/L, 95% CI = -0.26 to -0.12, p = 0.02].

The investigators concluded large randomized controlled trials (RCTs) of at least 6 months duration with carbohydrate restriction, particularly 50 g/d carbohydrates, is superior in improving HDL-cholesterol and triglycerides levels in overweight/obese adults when compared with low-fat diets. Dietary guidelines should consider carbohydrate restriction as an alternative dietary strategy for the prevention/management of dyslipidemia for populations with cardiometabolic risk.

Original title:
Effects of carbohydrate-restricted diets on low-density lipoprotein cholesterol levels in overweight and obese adults: a systematic review and meta-analysis by Gjuladin-Hellon T, Davies IG, […], Amiri Baghbadorani R.

Link:
https://www.ncbi.nlm.nih.gov/pubmed/30544168

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50 grams of carbohydrates per day corresponds to a diet with 10 En% carbohydrates.
The easiest way to follow a diet with 10 En% carbohydrates is to choose only meals/products with 10 En% carbohydrates.
However, the most practical way to follow a diet with 10 En% carbohydrates is all meals/products that you eat on a daily basis should contain on average 10 En% carbohydrates. Check here which products contain 10 En% carbohydrates.

Objectives:
Cocoa and dark chocolate (DC) have been reported to be effective for health promotion; however the exact effect of cocoa/dark chocolate on anthropometric measures have not been yet defined. Therefore, this review article has been conducted.

Has cocoa/dark chocolate supplementation positive effect on weight, BMI and waist circumference (WC)?   

Study design:
This review article included a total of 35 RCTs, investigating the effects of cocoa/dark chocolate on weight, BMI and waist circumference.

Results and conclusions:
The investigators found meta-analysis did not suggest any significant effect of cocoa/dark chocolate supplementation on:
-body weight [-0.108 kg, 95% CI = -0.262 to 0.046 p = 0.168]
-BMI [-0.014 kg/m², 95% CI = -0.105 to 0.077, p = 0.759] and
-WC [0.025 cm, 95% CI = -0.083 to 0.129, p = 0.640].

The investigators found, however, subgroup analysis revealed that weight and BMI were significantly reduced with ≥ 30g chocolate per day during 4-8 weeks.

Furthermore, supplementation of ≥ 30g chocolate per day during 4-8 weeks significantly reduced waist circumference in non-linear fashion [r = 0.042, p-nonlinearity = 0.008].

The investigators concluded that ≥ 30g chocolate per day during 4-8 weeks reduce weight, BMI and waist circumference.

Original title:
Does cocoa/dark chocolate supplementation have favorable effect on body weight, body mass index and waist circumference? A systematic review, meta-analysis and dose-response of randomized clinical trials by Kord-Varkaneh H, Ghaedi E, […], Shab-Bidar S.

Link:
https://www.ncbi.nlm.nih.gov/pubmed/29553824

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Objectives:
High potato intake has been suggested as a risk factor for the development of type 2 diabetes. Therefore, this review article has been conducted.

Does potato intake increase risk of type 2 diabetes?

Study design:
This review article included 6 prospective cohort studies with a total of 4,545,230 person-year of follow-up and 17,758 diabetes cases.

Results and conclusions:
The investigators found for every increment of 1 serving/day of total potato consumption a significantly increased risk of 20% [HR = 1.20, 95% CI = 1.13 to 1.127, p 0.001, I2 = 27.1%, p for heterogeneity = 0.23] for type 2 diabetes both in men en women.

The investigators found for 2 servings/day of total potato consumption a significantly increased risk of 44% [HR = 1.44, 95% CI = 1.28 to 1.63] for type 2 diabetes both in men en women.

The investigators found for 3 servings/day of total potato consumption a significantly increased risk of 74% [HR = 1.74, 95% CI = 1.45 to 2.09] for type 2 diabetes both in men en women.

The investigators found significant evidence of a non-linear association between total potato consumption and risk of type 2 diabetes [X2 = 17.5, p for linearity 0.001].

The investigators concluded that long-term high consumption of potato (each serving a day increase) is strongly associated with increased risk of type 2 diabetes. These findings suggest that diet-health policy may be of importance in the prevention of diabetes.

Original title:
Potato consumption and risk of type 2 diabetes: A dose-response meta-analysis of cohort studies by Bidel Z, Teymoori F, […], Nazarzadeh M.

Link:
https://www.ncbi.nlm.nih.gov/pubmed/30144898

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According to the USDA Dietary Guidelines a serving of potato is 1 cup diced, mashed or baked or 1 medium boiled potato.

 

Objectives:
Modifiable factors that reduce the burden of the metabolic syndrome (MetS), particularly plant-derived biomarkers, have been a recent focus of rising interest. Therefore, this review article has been conducted.

Do dietary carotenoids reduce risk of metabolic syndrome?  

Study design:
This review article included 11 cross-sectional studies.
Publication bias was absent and harvest plots indicated consistency upon replication for β-carotene and total carotenoid exposures.

Results and conclusions:
The investigators found dietary total carotenoids intake significantly reduced risk of metabolic syndrome with 44% [pooled OR = 0.66, 95% CI = 0.56-0.78, 1 SD ∼ 0.82 µmol/L, n = 5 studies]. This reduced risk was the strongest for β-carotene, followed by α-carotene and β-crypotoxanthin.

The investigators found no association between retinol (vitamin A from animal products) and risk of metabolic syndrome [pooled OR = 1.00, 95% CI = 0.88-1.13, 1 SD ∼ 2.14 µmol/L, n = 6 studies].

The investigators concluded that carotenoids, particularly β-carotene, followed by α-carotene and β-crypotoxanthin may reduce risk of metabolic syndrome. May reduce because this review article only included cross-sectional studies and no cohort studies.

Original title:
Carotenoids, vitamin A, and their association with the metabolic syndrome: a systematic review and meta-analysis by Beydoun MA, Chen X, [...], Canas JA.

Link:
https://www.ncbi.nlm.nih.gov/pubmed/30202882

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Objectives:
Several studies have been published about the effect of garlic on lipid profile and blood glucose in diabetic patients. Which, the results mostly contradict with each other. Therefore, this review article has been conducted.

Does garlic improve lipid profile and blood glucose in diabetic patients?

Study design:
This review article included 33 articles with a total of 1,273 individuals, with a mean of 39 samples per study.

Results and conclusions:
The investigators found the concentration of serum total cholesterol significantly decreased wih 16.87 mg/dL [95% CI = -21.01 to -12.73, p = 0.001] in the garlic group when compared with the placebo group.

The investigators found the concentration of serum LDL cholesterol (bad cholesterol) significantly decreased with 9.65 mg/dL [95% CI = -15.07 to -4.23, p = 0.001] in the garlic group when compared with the placebo group.

The investigators found the concentration of serum triglycerides significantly decreased with 12.44 mg/dL [95% CI = -18.19 to -6.69, p = 0.001] in the garlic group when compared with the placebo group.

The investigators found the concentration of serum HDL cholesterol (good cholesterol) significantly increased with 3.19 mg/dL [95% CI = 1.85 to 4.53, p = 0.001] in the garlic group when compared with the placebo group.

The investigators found the concentration of serum fasting blood sugar significantly decreased with 10.90 mg/dL [95% CI = -16.40 to -5.40, p = 0.001] in the garlic group when compared with the placebo group.

The investigators found the concentration of serum HbA1c significantly decreased with 0.60 mg/dL [95% CI = -0.98 to -0.22, p = 0.001] in the garlic group when compared with the placebo group.

The investigators concluded that garlic improves lipid profile as well as glucose parameters and can be therapeutically effective in patients suffering from cardiovascular diseases and diabetes.

Original title:
The effect of garlic on lipid profile and glucose parameters in diabetic patients: A systematic review and meta-analysis by Shabani E, Sayemiri K and Mohammadpour M.

Link:
https://www.ncbi.nlm.nih.gov/pubmed/30049636

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Objectives:
What are the effects of ginger intake on weight loss, glycemic control and lipid profiles among overweight (BMI>25) and obese (BMI>30) subjects?

Study design:
This review article included 14 RCTs with in total of 473 subjects.

Results and conclusions:
The investigators found that supplementation with ginger significantly decreased among overweight (BMI>25) and obese (BMI>30) subjects:
-body weight (BW) [SMD -0.66, 95% CI = -1.31 to -0.01, p = 0.04];
-waist-to-hip ratio (WHR) [SMD = -0.49, 95% CI = -0.82 to -0.17, p = 0.003];
-hip ratio (HR) [SMD = -0.42, 95% CI = -0.77 to -0.08, p = 0.01];
-fasting glucose [SMD = -0.68, 95% CI = -1.23 to -0.05, p = 0.03] and;
-insulin resistance index (HOMA-IR) [SMD= -1.67, 95% CI = -2.86 to -0.48, p = 0.006].

The investigators found that supplementation with ginger significantly increased HDL-cholesterol (good cholesterol) levels [SMD = 0.40, 95% CI = 0.10 to 0.70, p = 0.009] among overweight (BMI>25) and obese (BMI>30) subjects.

The investigators found, however, that supplementation with ginger had no detrimental effect on:
-body mass index (BMI) [SMD = -0.65, 95% CI = -1.36 to 0.06, p = 0.074];
-insulin [SMD = -0.54, 95% CI = -1.43 to 0.35, p = 0.23];
-triglycerides [SMD = -0.27, 95% CI = -0.71 to 0.18, p = 0.24];
-total cholesterol [SMD = -0.20, 95% CI = -0.58 to 0.18, p = 0.30] and;
-LDL-cholesterol [SMD = -0.13, 95% CI = -0.51 to 0.24, p = 0.48].

The investigators concluded that ginger intake reduces body weight, waist-to-hip ratio, hip ratio, fasting glucose and insulin resistance index and increases HDL-cholesterol (good cholesterol), but has no affect on insulin, BMI, triglycerides, total- and LDL-cholesterol (bad cholesterol) levels among overweight and obese subjects.

Original title:
The effects of ginger intake on weight loss and metabolic profiles among overweight and obese subjects: A systematic review and meta-analysis of randomized controlled trials by Maharlouei N, Tabrizi R, […], Asemi Z.

Link:
https://www.ncbi.nlm.nih.gov/pubmed/29393665

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Persons with overweight are advised to choose products/meals with maximum 30 En% fat, maximum 7 En% saturated fat, maximum 0.2 grams salt per 100 kcal and minimum 1.5 grams fiber per 100 kcal. Check here which products/meals are suitable for persons with overweight.
 

Objectives:
The purpose of this review article is to review previously published meta-analyses on the effectiveness of dietary fiber on type 2 diabetes.

Study design:
This umbrella review article included 16 meta-analyses.

Results and conclusions:
The investigators found in the meta-analyses when comparing highest versus lowest dietary fiber intake, a statistically significant reduced risk of 15 to 19% [RR = 0.81-0.85] for type 2 diabetes. However, statistically significant heterogeneity was observed in all of these meta-analyses.

The investigators found in the meta-analyses when comparing highest versus lowest dietary cereal fibers, a statistically significant reduced risk of 13 to 33% [RR = 0.67-0.87] for type 2 diabetes. However, statistically significant heterogeneity was observed in all of these meta-analyses.

The investigators found in the meta-analyses of supplementation studies using β-glucan or psyllium fibers on type 2 diabetic participants, statistically significant reductions were identified in both fasting blood glucose concentrations and glycosylated hemoglobin percentages.

The investigators concluded that those consuming the highest amounts of dietary fiber, especially cereal fiber, may benefit from a reduction in the incidence of developing type 2 diabetes. May benefit because statistically significant heterogeneity was observed in all of these meta-analyses.
There also appears to be a small reduction in fasting blood glucose concentration, as well as a small reduction in glycosylated hemoglobin percentage for individuals with type 2 diabetes who add β-glucan or psyllium to their daily dietary intake.

Original title:
Dietary Fiber Intake and Type 2 Diabetes Mellitus: An Umbrella Review of Meta-analyses by McRae MP.

Link:
https://www.ncbi.nlm.nih.gov/pubmed/29628808

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Objectives:
The association between dietary protein intake and type 2 diabetes risk has been inconsistent in the previous epidemiological studies. Therefore, this review article (meta-analysis) has been conducted.

Is there an association between dietary protein intake and type 2 diabetes risk?

Study design:
This review article included 10 prospective cohort studies with a total of 34,221 type 2 diabetes cases.
No publication bias was detected.

Results and conclusions:
The investigators found after adjustment of potential confounders, a 5% of energy (5 En%) increment from dietary total protein intake was related to a significantly 9% [95 CI = 1.04-1.13, I2 = 42.0%] higher risk of type 2 diabetes. The results were robust in sensitivity analysis.

The investigators found after adjustment of potential confounders, a 5% of energy (5 En%) increment from dietary animal protein intake was related to a significantly 12% [95 CI = 1.08-1.17, I2 = 14.0%] higher risk of type 2 diabetes. The results were robust in sensitivity analysis.

The investigators found after adjustment of potential confounders, a significant U-shaped curve was observed for plant protein intake with the most risk reduction at about 6% of energy from plant protein intake [p nonlinearity = 0.001]. The results were robust in sensitivity analysis.

The investigators concluded that the consumption of protein, particularly animal protein increases risk of type 2 diabetes.

Original title:
Dietary protein intake and risk of type 2 diabetes: a dose-response meta-analysis of prospective studies by Zhao LG, Zhang QL, [...], Xiang YB.

Link:
https://www.ncbi.nlm.nih.gov/pubmed/29858629

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Objectives:
The association between coffee consumption and the level of C-reactive protein (CRP) has been evaluated in several epidemiological studies with conflicting results. Therefore, this meta-analysis (systematic review) has been conducted.

Does coffee consumption reduce level of C-reactive protein in humans?

Study design:
This review article included a total of 9 cross-sectional studies.

Results and conclusions:
The investigators found according to the combined standard mean difference (SMD) between the highest and the lowest coffee intake category, coffee consumption was associated with a significantly lower level of serum CRP level [SMD = -0.34, 95% CI = -0.62 to -0.06, p = 0.016].

The investigators found subgroup analysis for CRP marker showed that coffee consumption was associated with a significantly lower level of serum high-sensitivity CRP (hsCRP) [SMD = -0.51, 95% CI = -0.88 to -0.14, p = 0.007], but not standard CRP [SMD = 0.02, 95% CI = -0.28 to 0.32, p = 0.913].

The investigators concluded that coffee consumption is associated with a lower level of serum CRP, particularly serum high-sensitivity CRP. However, more well-designed prospective cohort studies are needed to elaborate the concerned issues further.

Original title:
Is coffee consumption associated with a lower level of serum C-reactive protein? A meta-analysis of observational studies by Zhang Y and Zhang DZ.

Link:
https://www.ncbi.nlm.nih.gov/pubmed/29405789

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Objectives:
Epidemiological studies exploring the role of flavonoids intake in preventing type 2 diabetes mellitus (T2DM) showed inconsistent results. Therefore, this review article (meta-analysis) has been conducted.

Does flavonoids intake decrease risk of developing type 2 diabetes?

Study design:
This review article included 10 independent cohorts published between 2002 and 2017 with a total of 312,015 participants, of which 19,953 type 2 diabetes cases were identified during the follow-up periods from 4 to 28 years.
All participants were free of type 2 diabetes at baseline (at the beginning of the study), with age ranging from 28 to 75 years.
Dietary flavonoids intake was evaluated using food-frequency questionnaire and type 2 diabetes was frequently ascertained through medical records.
In the original studies, the median intake level of total flavonoids was 8.9 to 501.8 mg/day for the lowest categories and 33.2 to 1452.3 mg/day for the highest categories.
The most commonly adjusted variables included age, sex, total energy intake, body mass index, smoking, alcohol consumption and physical activity.
All included studies had a NOS score of ≥7, with an average score of 7.9, indicating the presence of high methodological quality.

There was no indication of publication bias from visual inspection of the funnel plot, which was further confirmed by Egger test [p = 0.253].

Results and conclusions:
The investigators found when compared with the lowest intake, the highest intake of total flavonoids was associated with a significantly 9% decreased risk of type 2 diabetes [RR = 0.91, 95% CI = 0.86-0.96, I2  =  21%, p =  0.257].
In stratified analyses, the pooled RR for total flavonoids intake was not modified by sample size, sex, follow-up duration and study location.
Leave-one-out sensitivity analysis showed that no individual study had a significant influence on the final result.

The investigators found in subgroup analyses when compared with the lowest intake, the highest intake of anthocyanidins significantly decreased risk of type 2 diabetes with 11% [RR = 0.89, 95% CI = 0.82-0.95].

The investigators found in subgroup analyses when compared with the lowest intake, the highest intake of flavan-3-ols significantly decreased risk of type 2 diabetes with 14% [RR = 0.86, 95% CI = 0.78-0.95].

The investigators found in subgroup analyses when compared with the lowest intake, the highest intake of flavonols significantly decreased risk of type 2 diabetes with 14% [RR = 0.86, 95% CI = 0.80-0.94].

The investigators found in subgroup analyses when compared with the lowest intake, the highest intake of isoflavones significantly decreased risk of type 2 diabetes with 9% [RR = 0.91, 95% CI = 0.84-0.98].

The investigators found in 9 cohort studies a curvilinear relationship between total flavonoids intake and type 2 diabetes risk [p for nonlinearity = 0.042] with a significant risk reduction at an intake of ≥550 mg/day.

The investigators found when assuming a linear association, the risk of type 2 diabetes was reduced by 5% [RR = 0.95, 95% CI = 0.93-0.97] for each 300-mg/day increment in total flavonoids intake.

The investigators concluded that intakes of total flavonoids, particularly ≥550 mg/day, anthocyanidins, flavan-3-ols, flavonols and isoflavones are associated with significantly decreased risks of type 2 diabetes in the highest versus lowest analyses. Additionally, the dose-response analysis suggest a curvilinear relationship of total flavonoids intake with type 2 diabetes risk; when assuming a linear manner, the risk of type 2 diabetes is reduced by 5% for an increment of 300 mg/day in total flavonoids intake.

Original title:
Flavonoids intake and risk of type 2 diabetes mellitus: A meta-analysis of prospective cohort studies by Xu H, Luo J, [...], Wen Q.

Link:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5959406/

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Objectives:
There is an increasing trend in the consumption of poor-quality diets worldwide, contributing to the increase of non-communicable diseases. Diet directly influences physiological composition and subsequently physical health. Studies have shown that dietary macronutrient and energy content can influence the proportion of intramuscular fat (IMF), which mediates various metabolic and endocrine dysfunction. Therefore, this review article has been conducted.

Do different types of dietary macronutrient intake increase the proportion of intramuscular fat?

Study design:
This review article included 13 trials (RCTs, quasi-RCTs, controlled trials, randomized controlled crossover trials or controlled crossover trials).

High-fat diets were diets with a proportion of fat between 38 and 85 En%. Participants in high-fat diets were all young to middle aged adults with ages varying between 18 and 50 years.

Participants in starvation diets (a decrease of 25% calorie from weight maintenance energy requirements) and hypocaloric diets (890 calories per day, until 15% weight reduction) followed the diet for 8 days with a 3-week washout period in between.

Cohen’s criteria were used to determine the effect size of SMDs, where a SMD between 0.2 and 0.5 is small, a SMD between 0.5 and 0.8 is moderate and a SMD above 0.8 is large. SMDs below 0.2 were considered unsubstantial.

Results and conclusions:
The investigators found in 6 studies with in a total of 134 participants receiving a high-fat intervention and 135 people receiving a control intervention, that high-fat diets (38 and 85 En% fat) significantly increased the proportion of intramuscular fat [SMD = 1.24, 95% CI = 0.43-2.05, p  = 0.003, I2 = 87%].  
Sensitivity analysis (excluding studies with a quality value 20, smallest sample size 8 and those that do not specify participant characteristics) showed a significantly SMD of 1.26 [95% CI = 0.23-2.28, p = 0.02]. 

The investigators found diets with an increased proportion of carbohydrates decreased the proportion of intramuscular fat.
However, increasing caloric intake with carbohydrates compared to a standardized diet (55 En% carbohydrates, 30 En% fat and 15 En% protein) increased the proportion of intramuscular fat.

The investigators found starvation diets (a decrease of 25% calorie from weight maintenance energy requirements) increased intramuscular fat stores and hypocaloric diets (890 calories per day, until 15% weight reduction) did not result in any intramuscular fat proportion changes.

The investigators concluded that high-fat diets (38 y 85 En%), excessive caloric intake in the form of carbohydrates and short-term starvation diets are associated with increases in the proportion of intramuscular fat. However, further studies are needed to assess the effects of macronutrient combinations on intramuscular fat and the influence of diet-induced intramuscular fat alterations on health outcomes. In addition, intramuscular fat poses a possibly effective clinical marker of health.

Original title:
The Effects of Diet on the Proportion of Intramuscular Fat in Human Muscle: A Systematic Review and Meta-analysis by Ahmed S, Singh D, [...], Kumbhare D.

Link:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5826234/

Additional information of El Mondo:
Find more information/studies on fat and carbohydrates consumption and diabetes right here.

Higher intramuscular fat levels are positively associated with insulin resistance and an increased risk of developing type 2 diabetes.

Objectives:
Observationally, homocysteine is associated with higher risk of diabetes. Folate, which reduces homocysteine, is promising for the prevention and treatment of diabetes. Previous meta-analysis (review) of 3 trials suggested folate might lower hemoglobin A1c (HbA1c). Therefore, this review article (meta-analysis) has been conducted.

Have folic acid supplementation positive effects on insulin resistance and glycemic control, like HbA1c level and fasting glucose level?

Study design:
This review article included 18 RCTs with in total of 21,081 people with/without diabetes.

Results and conclusions:
The investigators found that folic acid (folate) supplementation significantly reduced fasting glucose level with 0.15 mmol/L [95% CI = -0.29 to -0.01]. Significant means that there is an association with a 95% confidence.

The investigators found that folic acid (folate) supplementation significantly reduced homeostatic model assessment-insulin resistance (HOMA-IR) with 0.83 [95% CI = -1.31 to -0.34].

The investigators found that folic acid (folate) supplementation significantly reduced fasting insulin level with 1.94 μIU/mL [95% CI = -3.28 to -0.61].

The investigators found that folic acid (folate) supplementation had no clear effect on diabetes or HbA1c level.

The investigators concluded that folic acid (folate) supplementation reduces both fasting glucose level, fasting insulin level and homeostatic model assessment-insulin resistance (HOMA-IR) but it has no effect on diabetes or HbA1c level.

Original title:
The effects of folate supplementation on glucose metabolism and risk of type 2 diabetes: a systematic review and meta-analysis of randomized controlled trials by Zhao JV, Schooling CM and Zhao JX.

Link:
https://www.ncbi.nlm.nih.gov/pubmed/29501221

Additional information of El Mondo:
Find more information/studies on diabetes and folic acid right here.

Patients with diabetes often have both an increased fasting glucose level, HOMA-IR value and fasting insulin level.

Objectives:
The increasing prevalence of diabetes in the United Kingdom and worldwide calls for new approaches to its management and diets with low glycaemic index have been proposed as a useful means for managing glucose response. However, there are conflicting reports and differences in the results of studies in terms of their effectiveness. Furthermore, the impact of low-glycaemic index diets (low GI-diets) and their long-term use in patients with type 2 diabetes remains unclear. Therefore, this review article (meta-analysis) has been conducted.

Do patients with type 2 diabetes mellitus benefit from low-GI diets?

Study design:
This review article included 6 RCTs.

Results and conclusions:
The investigators found in 2 RCTs that low-glycaemic index (low-GI) diet resulted in a significant improvement in glycated haemoglobin (HbA1c) [0.05]:
low-GI diet Δ = -0.5% [95% CI = -0.61% to -0.39%] vs. high-cereal fibre diet Δ = -0.18% [95% CI = -0.29% to -0.07%] and;
low-GI legume diet Δ = -0.5% [95% = -0.6% to -0.4%] vs. high-wheat fibre diet Δ = -0.3% [95% Cl = -0.4 to -0.2%].

The investigators found in 4 RCTs significant improvements in fasting blood glucose in low-GI diets compared to higher-GI diets or control:
low-GI diet = [150.8 ± 8.7] vs. higher-GI diet = [157.8 ± 10.4 mg/dL, mean ± SD, p = 0.43];
low-GI diet = [127.7] vs. high-cereal fibre diet = [136.8 mg/dL, p = 0.02];
low-GI diet = [6.5 (5.6-8.4)] vs. standard diabetic diet = [6.7 (6.1-7.5 mmol/L), median and interquartile range p > 0.05] and;
low-GI diet = [7.3 ± 0.3] vs. conventional carbohydrate exchange diet = [7.7 ± 0.4 mmol/L, mean ± SEM (Standard Error of Mean), p 0.05].

The investigators concluded that the low-GI diet is more effective in controlling glycated haemoglobin (HbA1c) and fasting blood glucose compared with a higher-GI diet or control in patients with type 2 diabetes. It will useful to evaluate the long-term effectiveness of low-glycaemic index diet in patients with type 2 diabetes.

Original title:
The Effect of Dietary Glycaemic Index on Glycaemia in Patients with Type 2 Diabetes: A Systematic Review and Meta-Analysis of Randomized Controlled Trials by Ojo O, Ojo OO, [...], Wang XH.

Link:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5872791/

Additional information of El Mondo:
Find more information/studies on diabetes and GI-diets right here.

A low-GI diet is a diet with a lot of products/meals with a low GI.
Products/meals with a low GI are products/meals with a GI-number of 55 or less.
In daily life, products/meals with a low GI contain at least 1.5 grams fiber per 100 kcal. These products and meals contain at least 1.5 grams fiber per 100 kcal.
 

Objectives:
Type 2 diabetes mellitus (T2DM) is one of the most important public health issues. Vitamin K supplementation might have favorable effect on risk factors of T2DM. Therefore, this review article (meta-analysis) has been conducted.

Have vitamin K supplementation favorable effects on risk factors of type 2 diabetes mellitus?

Study design:
This review article included 5 RCTs with in total of 533 participants.

There was no evidence of publication bias.

Results and conclusions:
The investigators found overall, meta-analysis did not show any beneficial effect of vitamin K supplementation on both:
-fasting blood sugar levels [-0.91 mg/dL, 95% CI = -2.57 to 0.76, p = 0.28];
-fasting insulin levels [-0.35 μIU/mL, 95% CI = -1.70 to 1.00, p = 0.61];
-HOMA-IR [-0.06, 95% CI = -0.32 to -0.19, p = 0.63] and
-2-h oral glucose tolerance test [-4.00 mg/dL, 95% CI = -20.00 to 11.99, p = 0.62].

The investigators found sensitivity analysis showed that overall estimates were not affected by elimination of any study.

The investigators concluded that vitamin K supplementation has no significant effect on glycemic control in healthy subjects. However, further studies should be performed on diabetic and pre-diabetic patients to determine the effect of vitamin K supplementation on impaired glycemic control.

Original title:
Effect of Vitamin K Supplementation on Glycemic Control: A Systematic Review and Meta-Analysis of Clinical Trials by Shahdadian F, Mohammadi H and Rouhani M.

Link:
https://www.ncbi.nlm.nih.gov/pubmed/29523009

Additional information of El Mondo:
Find more information/studies on diabetes and vitamin K right here.
 

Objectives:
The actual effects of L-carnitine administration on leptin serum level is inconsistent. Therefore, this review article (meta-analysis) has been conducted.

Does L-carnitine supplementation reduce leptin serum level?

Study design:
This review article included 7 RCTs with 325 cases (group with L-carnitine administration) and 330 controls (group without L-carnitine administration).

Subgroup analysis to find the sources of heterogeneity showed that L-carnitine dosage [ 2 g: I2 = 00.0%, p = 0.408] and study population [diabetes: I2 = 46.7%, p = 0.153 and non-diabetes: I2 = 15.1%, p = 0.317] were the potential sources of heterogeneity.

Results and conclusions:
The investigators found that L-carnitine supplementation had no significant effect on serum leptin concentrations [WMD = -0.565 ng/mL, 95% CI = -2.417 to 1.287, p = 0.550, I2 = 84.3%, p  0.0001].

The investigators found in subgroup analysis that  ≥ 2 mg L-carnitine supplementation significantly reduced serum leptin concentrations [WMD = -2.742 ng/mL, 95% CI = -3.039 to -2.444, p  0.001].

The investigators found in subgroup analysis that L-carnitine supplementation significantly reduced serum leptin concentrations in diabetic patients [WMD = -2.946 ng/mL, 95% CI = -3.254 to -2.638, p  0.001].

The investigators found in subgroup analysis that L-carnitine supplementation during 12 weeks significantly reduced serum leptin concentrations [WMD = -2.772 ng/mL, 95% CI = -3.073 to -2.471, p  0.001].

The investigators concluded that at least 3 mg L-carnitine per day in the course of 12 weeks reduce serum leptin concentrations, especially in diabetic patients.

Original title:
The effect of L-carnitine supplementation on serum leptin concentrations: a systematic review and meta-analysis of randomized controlled trials by Nazary-Vannani A, Ghaedi E, […], Varkaneh HK.

Link:
https://www.ncbi.nlm.nih.gov/pubmed/29453657

Additional information of El Mondo:
Find more information/studies on diabetes and L-carnitine and diabetes right here.

L-carnitine is a non-essential amino acid, which is also found in foods.

Objectives:
Does vegetable and/or fruit consumption reduce metabolic syndrome (MetS)?

Study design:
This review article included 20 cross-sectional studies, 1 case-control study and 5 cohort studies.

Results and conclusions:
The investigators found in 16 studies when comparing the highest versus the lowest category of vegetable consumption a significantly reduced risk of 11% [overall multivariable-adjusted RR = 0.89, 95% CI = 0.85-0.93, p 0.001] for metabolic syndrome.

The investigators found in 16 studies when comparing the highest versus the lowest category of fruit consumption a significantly reduced risk of 19% [overall multivariable-adjusted RR = 0.81, 95% CI = 0.75-0.88, p 0.001] for metabolic syndrome.

The investigators found in 8 studies when comparing the highest versus the lowest category of vegetable and fruit consumption a significantly reduced risk of 25% [overall multivariable-adjusted RR = 0.75, 95% CI = 0.63-0.90, p = 0.002] for metabolic syndrome.

The investigators concluded that vegetable and/or fruit consumption is negatively associated with metabolic syndrome. However, more well-designed prospective cohort studies are needed to elaborate the concerned issues further.

Original title:
Associations of vegetable and fruit consumption with metabolic syndrome. A meta-analysis of observational studies by Zhang Y and Zhang DZ.

Link:
https://www.ncbi.nlm.nih.gov/pubmed/29506604

Additional information of El Mondo:
Find more information/studies on overweight and fruit and vegetable consumption right here.